A Yemeni national, released from the U.S. military prison in Guantanamo Bay, is welcomed by his family upon his arrival in Riyadh. (Agence France-Presse via Getty Images)

The United States has sent four Yemeni prisoners from the facility at Guantanamo Bay to Saudi Arabia, the Pentagon said Thursday, part of a final rush to resettle detainees before the Trump administration clamps down on movements out of the prison.

The inmates include Muhammad Ali Abdullah Muhammad Bawazir, whose treatment during a lengthy hunger strike was addressed in a federal court case; Salem Ahmad Hadi Bin Kanad, who was shot during an Afghanistan prison riot in 2001 but later recovered; and Mohammed Rajab Sadiq Abu Ghanim and Abdallah Yahya Yusif Al-Shibli. The prisoners had been held since as early as January 2002.

Family members held an emotional reunion with the prisoners Thursday at the airport in Riyadh, Reuters reported.

“The United States is grateful to the government of the Kingdom of Saudi Arabia for its humanitarian gesture and willingness to support ongoing U.S. efforts to close the Guantanamo Bay detention facility,” the Pentagon said in a statement. Congress has barred the United States from repatriating prisoners to Yemen, mired in a lengthy civil war, and other countries where there are security concerns.

The transfers represent the culmination of years of effort by Obama administration officials to scale back operations at the detention center. While President Obama failed to close the prison as he promised at the outset of his administration, he dramatically reduced the inmate population. After the transfer announced Thursday, the number of inmates stands at 55, far below its peak under George W. Bush of more than 700.

President-elect Donald Trump has vowed to block transfers after he takes office Jan. 20. Administration officials have notified Congress of their plans to resettle as many as 15 additional prisoners before Trump’s inauguration.

Republicans have long opposed detainee resettlements, fearing released prisoners could plot against Americans, and have moved to restrict them. Earlier this week, Trump tweeted that no further releases should be allowed. “These are extremely dangerous people and should not be allowed back onto the battlefield,” he wrote.

Detainee advocates have praised the Obama administration for moving prisoners — most of whom have never been charged with a crime — out of Guantánamo, but criticized the president for not acting unilaterally to shutter the facility over congressional objections.

Many resettled prisoners, some of whom suffer from serious health problems, have struggled to adapt to life in new countries after their lengthy detentions. Earlier this year, Bawazir declined an opportunity to be resettled in a European country, concerned about moving to a non-Muslim country where he knew few people. His lawyer, John A. Chandler, said Bawazir had numerous family members in Saudi Arabia, and felt more comfortable with resettlement there.

It wasn’t immediately clear whether the released detainees would take part in a rehabilitation program run by the Saudi government.

Julie Tate contributed to this report.